Process of preserving wood.



1 UNITED. STATES PATENT orrion;

JOHN M. NELSON, 33., OF SHERWOOD, MARYLAND.

PRQCESS 0F PRESERVING WOOD.

No Drawing.

. Specification of Letters Patent. Patented Oct. 12, 1909. Application filed m 1, 190a. Serial No. 441,513.

To all whom'it may concern: i I

Be it known that 1, JOHN M. NELSON, J r.,

a citizen of the United States, and an employee of the Forest Service, Department of Agriculture, a legal resident of the State of Maryland, residing-at Sherwood, county, of Baltimore, Maryland, (whose post-oifice address is Forest Service, Department of Agriculture, Washington, District of Columbia,) have invented new and useful Improvements in the Process of the Treatment of Timber with Liquid Preservatives, and made application by petition of even date herewith, under the act of March 3, 1883, chapter 143, 22 Stat, 625, praying that Letters Patent therefor may be granted to me.

- The invention herein described'and claimed may be used by the Government of the United States or any of its oflicers or emtioned.

The object of the improved process is to secure a deeper penetration of the wood with a smaller amount of the preservative than is obtained by the methods commonly in use.

"The process of treatment consists in immersing the wood in a first bath of suitable preservative or non-preservative liquid,

which bath is above the temperature of boiling-water, In this baththe wood becomes heated and the air and moisture contained vwithin it are expanded and a portion of a second bathof preservative liquid, which] is at a temperature below-that of boiling them driven out of the wood, the action extending to adepth which depends upon:

the degree of heat used and the time for which the timber is left in the bath; At the s end ofv a suflicient time, the wood is freed r from the unabsorbed portion of the preservativeoor' non-preservative liquid of the first, or hot bath, and immediately immersed in detail Water-, or the wood is left in the preservative liquid of the first bath, which is cooled to a temperature below that of boiling water to constitute the second bath. In either case amount which is so drawn in, and the depth to which it penetrates depending upon the extent of the action which has been produced by the first, or hot bath, above described,,and the length of time the wood is left in the sec- 0nd, or cold bath. The wood isthen freed from the unabsorbed portion of the second, or cool bath and again subjected to a third bath of preservative or non-preservative liquid, whose temperature is above the boiling'point ofwater and preferably somewhat abovethe temperature of the first bath, care being exercised, however, that the temperature be not high enough in either case to injure the strength of the wood, or the wood is left in the preservative liquid of the first and second baths-which is raised to a temperature like that described above for "the third bath. The efl'ect of this third, or final hot bath is that any given amount of preservative liquid which has been drawn into the wood is distributed through a deeper zone, that is tosay, a deeper penetration of wood is secured with a smaller amount of thepreservative liquid than is ossible with the use of the first two baths on y, which has before been statedto vention. 1

The process embodied in this invention is applicable" to the preservative. treatment of be the object of this intlmber with liquid preservatives in any man- ,,ner, using closed cylinders, with or without pressure, or open tanks or vats. But it is especially adapted for use with what is known as the ,open-tarikproeess. To explain'it more specifically, therefore, I will describe its applicationv to this process in First, a s applied toheavy timbers: The timber is first submerged in a preservative or non-preservative liquid in an open tank,

which is. then heated to a temperature of I preservative or a nonpreservative liquid may about 220 ll, constituting the first bath. This tenqaerature is maintained for a period of about two hours. The temperature of the preservative is then lowered. constitutingthe second bath, to 150 Fl, or until the timber has absorbed 5 pounds of the preservative per cubic foot, or such amount as may be necessary to obtain the desired pene: tration. The temperature of a preservative or non-preservative is then raised to about 230 l*.,constituting the third bath, and is there held for a period of approxin'iately 3 hours, when the timber, while still hot, is

taken out of-the preservative-in a treated condition.-

Second, as applied to light timbers: The timber is submerged in a-preservative or non-preservative liquid. in an open tank, which is heated, and thereafter cooled, to the same degrees of temperature and for the same periods of time as above described for heavy timbers; or, the timber may be transferred, at the end of the first hot bath period ,to another tank containing cold preservative,

constituting the second bath, until the desired impregnation is secured. It is then returned to the heated preservatlve or nonpreservativeliquid of the first bath, which has, in the meantime, been raised to a temperature of about 230 F., constituting the third bath, and is there held for a period of three hours, at the end of which time the timber, whilestill hot, is taken out of the preservative or.non-preservative in a treat/ed condition. I

.The essential feature of my invention is the successive immersion of wood in a preservative or non-preservative liquid heated above the boiling point of water, then in-preservative liquid at a temperature below the boiling pointof water, and finally, again in preservative or non-preservative liquid heatedabove the boiling point of water and preferably-somewhat hotter'than the liquid of the first immersion.

I have above illustrated the. process as applied to the use of two separate and distinct tanks containing hot and cold liquids respectively, or of a singletank in which the liquid is successively-heated and cooled; but my invention may be applied with equal success with any other method of manipulating the liquids 'to obtain the desired end, as well as with closed tanks or cylinders.

\Vhen a single tank is used, the liquid'may be cooled by artificial means if desired; 'or instead of cooling the liquid when the wood has been immersed for a suflicient time in the first, or hot bath,-this liquid may be drawnoff and its place supplied by cold liquid, which in turn may again be replaced y'ot.

In the processes above specified either a be used in the first bath; in the second bath av prcscrmtive liquid must be used, in the third bath a preservative or a nonpreservative liquid may be used. The preservative liquids used in my process may consist of such substances as creosote, crude petroleum,

and oil tar or. aqueous solutions of the following chemical salts ;zinc chlorid, sodium preservative or nonpreservative liquid or liquids whatever in carrying out the process described and specified.

What I claim, and desire to secure by Letters Patent is:

1. The method of preventing deterioration or decay of timber, which eonsists in first subjecting the timber to a suitable bath heated above the boiling point of water, second, lowering the temperatureof the bath, third raising the temperature to a point abovethat of the initial bath, and,finally, removing the timber from the liquid and allowing it to cool in the open air, substantially .as specified. Y

2. The method of preventing the deterioration and decay of timber wlnch consists in subjecting the timber to a suitable bath, heated to a temperature sufiicient to expand and drive off a portion of the gas and moisture contained 1n the timber, then lowering the temperature of the bath sufliciently to permit the absorption of the required amount of preservative into the timber, due to the contraction of the gases and moisture, then raising the temperature to a point, preferably slightly above that of the first bath in order that more of the gases and moisture in the interior of the timber may be driven'ofl", and finally submitting the timber to the action of the air, in order that the preservative in the exterior portions of the timber may be drawn farther into the timber, due to the contraction caused by the coolin of the atmosphere.

3. T e method of preserving timber and the like which consists in first subjecting the same to the action of a bath of a suitable liquid heated to a temperature of over 100 0., then to a bath of a suitable preservative liquid at a lower temperature, then to the action of a bath of a suitable li aid at a temperature at least as high as the rst bath, substantially as described.

4. The method of preserving timber and the like which consists in first subjecting the same to a bath of a suitable liquid at a temnesses, this twenty-fifth day'of April, 1908, perature of over 100 0., then lowering the at Washington, District of Columbia. temperature to permit absorption, then again T raising the temperature to disseminate the JOHN LELSONJR' absorbed liquid, substantially as described. Witnesses:

In testimony whereof I aflix my signature W. F. SHERFESEE,

in the presence of the two subscribed Wit- CHAS. R. PIERCE. 

